Enhanced file system failure tolerance

• US 20020174295A1
• Filed: 01/29/2002
• Published: 11/21/2002
• Est. Priority Date: 01/29/2001
• Status: Abandoned Application

• Current Assignee: Braodband Storage LLC, Snap Appliance, Inc. (Silicon Valley Technology Partners LLC)
• Original Assignee: Adaptec Incorporated (Steel Partners Holdings LP)
• Inventors: Schweitzer, James R., Bolstad, Gregory D., Staub, John R., Randall, Jay G., Priester, Wilbur George, Ulrich, Thomas R.
• Application Number:
  US10/060,919
• Publication Number:
  US 20020174295A1
• Time in Patent Office: Days
• US Class Current: 711/114
• CPC Class Codes: G06F 11/1076 Parity data used in redundant arrays of independent storages, e.g. in RAID systems
• CPC Class Codes: G06F 11/1471 involving logging of persistent data for recovery
• CPC Class Codes: G06F 11/2035 without idle spare hardware
• CPC Class Codes: G06F 11/2048 where the redundant components share neither address space nor persistent storage
• CPC Class Codes: G06F 11/2097 maintaining the standby controller/processing unit updated initialisation or re-synchronisation thereof G06F11/1658 and subgroups
• CPC Class Codes: G06F 16/10 File systems; File servers
• CPC Class Codes: G06F 2201/84 Using snapshots, i.e. a logical point-in-time copy of the data
• CPC Class Codes: G06F 2211/1028 Distributed, i.e. distributed RAID systems with parity
• CPC Class Codes: G06F 9/5083 Techniques for rebalancing the load in a distributed system

Abstract

An enhanced file system with failure tolerance is described. The enhanced file system includes a plurality of disk drives for storing parity groups, each parity group comprising storage blocks. The storage blocks include one or more data blocks and a parity block associated with the data blocks. Each of the storage blocks is stored on a separate disk drive such that no two storage blocks from a given parity group reside on the same disk drive. A recovery module dynamically recovers data lost when a disk drive becomes unavailable. The recovery module produces a reconstructed block by using information in the remaining storage blocks of a parity group corresponding to an unavailable storage block, and stores the reconstructed block on a functioning drive. The file system metadata is updated to indicate where the reconstructed block is stored.

Claims

1. A computer storage system, comprising:

a plurality of disk drives for storing parity groups, each parity group comprising storage blocks, said storage blocks comprising one or more data blocks and a parity block associated with said one or more data blocks, each of said storage blocks stored on a separate disk drive such that no two storage blocks from a given parity group reside on the same disk drive; and

a recovery module to dynamically recover data lost when at least a portion of one disk drive in said plurality of disk drives becomes unavailable, said recovery module configured to produce a reconstructed block by using information in the remaining storage blocks of a parity group corresponding to an unavailable storage block, store said reconstructed block on a functioning drive in said plurality of disk drives, and update file system metadata to indicate where said reconstructed block is stored.

2. The computer storage system of claim 1, wherein a size of a first parity group is larger than a size of a second parity group.

3. The computer storage system of claim 1, further comprising metadata to specify which disk drive in said plurality of disk drives contains a desired storage block.

4. The computer storage system of claim 1, wherein a size of a first parity group is larger than a size of a second parity group of the same file.

6. The computer storage system of claim 1, wherein said recovery module automatically learns of a disk failure and runs in a background process to reconstruct data lost as a result of said disk failure without disrupting normal file system operations.

5. The computer storage system of claim 23, wherein said recovery module runs in a background process during file system operations.

7. A method for storing data in a computer network, comprising:

determining a size of a parity group in response to a write request, said size describing a number of data blocks in said parity group;

arranging at least a portion of data from said write request according to said data blocks;

computing a parity block for said parity group;

storing each of said data blocks on a separate disk drive such that no two data blocks from said parity group reside on the same disk drive;

storing said parity block on a separate disk drive that does not contain any of said data blocks;

detecting a storage failure that renders a storage block unavailable as an unavailable storage block;

reconstructing lost data by using information in the remaining storage blocks of a parity group corresponding to said unavailable storage block to produce a reconstructed parity group.

8. The method of claim 7, further comprising storing metadata to describe a disk and logical block location of each of said data blocks and said parity block.

9. The method of claim 7, further comprising redistributing parity groups by combining a first parity group having a first size and a second parity group having a second size to produce a combined parity group having a third size, wherein said third size specifies a number of blocks that is, at most, one less than the number of disk drives available to store data from said parity group.

10. The method of claim 7, wherein said reconstructing occurs during normal file system operations without disrupting said normal file system operations.

11. A computer storage system, comprising:

a plurality of disk drives for storing parity groups, each parity group comprising storage blocks, said storage blocks comprising one or more data blocks and a parity block associated with said one or more data blocks, each of said storage blocks stored on a separate disk drive such that no two storage blocks from a given parity group reside on the same disk drive; and

means for detecting a storage failure;

means for recovering data lost due to said storage failure by reconstructing a lost storage block of a parity group using information in the available storage blocks of said parity group to produce a reconstructed block, storing said reconstructed block and updating file system metadata to indicate where said reconstructed block is stored.